Ringberg ISM 2021

Cluster formation and fragmentation (CMF, IMF) ... or maybe more scattered questions about HMYSOs


Adam Ginsburg

Assistant Professor
Department of Astronomy
University of Florida, Gainesville

  • Postdoc: Allison Towner
  • PhD: Desmond Jeff, Theo Richardson, Alyssa Bulatek, Nazar Budaiev
  • REU: Justin Otter, Danielle Bovie, Josh Machado, Sydney Petz
  • Undergrad: Madeline Hall, Michael Fero, Derod Deal, Parker Ormonde, Aden Dawson, Helen Radomski, Brice Tingle, Oketa Basha, Morgan Himes
Slides available at https://keflavich.github.io/talks/RingbergISM2021.html

Questions about HMYSOs & clusters:

  • How dense are forming clusters? (stellar density)
    • Dense enough to form high-mass stars by collisions?
    • Possible approach: ALMA-LB observations
  • How massive are YSOs?
    • Luminosity, dust-mass estimates are really bad
    • Possible approach: Dynamical mass measurements. Salt disks? Masers?
  • Do HMYSOs get their mass through disks?
    • We see disks, but mostly they have little mass compared to the stars
    • Competitive accretion? Inertial inflow? Collisions?

How dense are cluster-forming regions?

OMC1 is denser than the ONC

N*OMC(Otter+ 2021) = 1.6 x 105 pc-3
N*ONC(Otter+ 2021) = 0.6 x 105 pc-3
N*ONC(Hillenbrand+ 1998) = 0.2 x 105 pc-3

Many new disks in the OMC

Otter+, resubmitted
FOV: 0.07 pc (16000 AU)
72 YSOs
One "hot core"

Disk Gallery

Salts in Orion

Orion Source I
a disk around a 15 M⊙ YSO

Salt: NaCl
Image: Ginsburg, NRAO
Left: Tanaka+ 2020, pair of NaCl-bearing disks.
Right: G17, Maud+ 2020

Temperature?

Temperature?

A contrived model

Observing the Keplerian rotation profile of a disk is the most direct way to measure a protostar's mass

(we can only see the disk, not the star itself)

W51 e2e: Too optically thick at 1mm to measure disk

Goddi+ 2020

CS v=0 J=1-0 and v=0 J=2-1 masers trace the disk?

Ginsburg+ 2019

CS maser conditions

van der Walt+ 2020
  • Top: CS J=1-0, Bottom: CS J=2-1
  • Red: Consistent w/W51e2e observations
  • Masers do not coexist; require different specific CS column
    (N2-1=1015.6, N1-01016.1 cm-2)
  • Require high abundance (XCS > 10-5)
  • Hot (300-500 K), moderate-density (n~105 cm-3): Disk surface? Or outflow cavity wall?

We can use salts to measure HMYSO masses

  • NaCl, KCl are only in the disk, not the outflow
    (water traces both)
  • NaCl is detected in at least two other HMYSOs
    (Tanaka+ 2020, Maud+ in prep)
  • Salts are observable with ALMA, the JVLA, and the future ngVLA
  • Future projects will involve observing and modeling salt disks to measure HMYSO masses

Zooming in: W51-IRS2

Zooming in: W51-IRS2

Zooming in: W51-IRS2

Goddi+ 2020: The outflow (& disk) around W51 North changed direction by ~50 deg in < 100 years.

Questions about HMYSOs & clusters:

  • How dense are forming clusters? (stellar density)
    • Dense enough to form high-mass stars by collisions?
    • Possible approach: ALMA-LB observations
  • How massive are YSOs?
    • Luminosity, dust-mass estimates are really bad
    • Possible approach: Dynamical mass measurements. Salt disks? Masers?
  • Do HMYSOs get their mass through disks?
    • We see disks, but mostly they have little mass compared to the stars
    • Competitive accretion? Inertial inflow? Collisions?